I can't figure out how to do the fancy quoty thing but here's what Mr GDT said in the Totalfilm article.

"Well, they are the progeny of Shelob, but Shelob was quite a promiscuous girl [laughs]. She mated with many partners. And insects and spiders are incredibly adaptable creatures. There will be spiders… [Laughs] That sounds like a Paul Thomas Anderson sequel: There Will Be Spiders! But they are visually quite striking and in a different way to Shelob.

I wish I could tell you more but I would be spoiling it again. They are very different. They are more creatures of the shadow, more creatures of the deep forest. They are not earth nesting. They are nesting in the canopies so physically they have adapted to that environment."

Oooh, oooh.... and he also says in his post that he personally crafted the appendages (or something) that go on his face and hands and if the spiders are nesting in the canopies they need claws to climb the trees. Did you know that all spiders have two claws on their feet but web-spinning ones have three? As if they weren't creep enough already. And Mr GDT is afraid of spiders so maybe this is a way of overcoming his fear.